T206 Cobb (Red) Polar Bear back inking question

[steve B]

Originally Posted by Jobu

I have seen PBs like this before. I usually attribute it to a poorly-inked and/or worn out blanket (used to print the cards) though I am not an expert so that might not be correct. Perhaps Steve B will weigh in.

Most likely it's caused by a worn plate. A worn blanket gives a totally different look, one I'm pretty sure I haven't seen on a card.

The plate for T206s was probably a limestone block. The surface will hold a fair amount of water, enough to repel ink. Depending on the exact process the area that you want to print gets coated with a substance that will retain ink. So when the plate is inked only what should print gets ink. That coating has a slight thickness. Over time some of it will wear off, thinner lines being the first to go.

Too much water can also cause this, but usually affects the rest of the design too.

The opposite problem is seen sometimes on Piedmont backs, if the plate is too dry, small areas that shouldn't retain ink and print causing areas between some of the fine lines to get filled in.

Steve B